Picture this: You wake up in the middle of the night, and you’re right in the middle of getting it on with your partner. Sounds like an unlikely—albeit pretty awesome—scenario, right?
Actually, according to recent Canadian research, up to 11 percent of men have had sex (or at least tried to) while they were asleep.
These nocturnal horndogs may masturbate, fondle, dry hump, and even perform oral or have full-on intercourse—all while they’re totally zonked out, according to another Canadian study. They usually only find out about it when they wake up mid-act, or hear the story from their wives or girlfriends the next morning.
Sleep doctors officially recognized the phenomenon this year when they added a new condition to their international diagnostic manual: “Sleep Related Abnormal Sexual Behaviors.” Most people refer to it as “sleep sex” or “sexsomnia,” but our favorite term was coined by one Reddit commenter: “Nightbang.”
Whatever you call it, we have one question: How can you be capable of sex when you’re unconscious?
Think of it as another form of sleepwalking, says Michel Cramer Bornemann, M.D., lead investigator at Sleep Forensics Associates in Minnesota.
When your brain transitions between different stages of sleep, sometimes neurons can misfire, he says. The error accidentally switches part of your brain “on” while the rest of it is still passed out. Those misfires happen in the part of your brain that controls your most basic human functions, Dr. Cramer Bornemann says.
“There are primal behaviors deep seated in the brain,” he says. “They’re simple motions necessary for survival, like defensive posturing and chewing. Of course, that includes sexual copulation and pelvic thrusting.”
In other words, your caveman brain is awake, grinding up against your girlfriend. Meanwhile, your sophisticated 21st century brain, capable of long division and artfully seducing her, has clocked out for the night.
Nightbang can happen to anyone, Dr. Cramer Bornemann says. Women, too: Up to 4 percent of females have had a sleep sex episode.
If you’re dubious that the rest of your brain could really be asleep, there’s proof: Researchers have video of a woman masturbating while her head is hooked up to an EEG showing she’s unconscious.
Sexsomnia is often instigated by coming into contact with your partner in bed, researchers say. Stress, fatigue, poor sleep, and medications like Ambien can also contribute.
It has nothing to do with naughty dreams, Dr. Cramer Bornemann says, or being unhappy with your waking sex life. It’s essentially just a brain fart. A weird, kinky brain fart.
For committed couples, sleep sex can be harmless, even entertaining. But it can also cause problems: Because you’re not actually conscious and in control, your sexual advances could be aggressive or inappropriate.
In rare cases, sexsomnia can result in assault. It can also strain a relationship—like if your wife thinks it’s evidence of sexual frustration or dreaming about other women. Or if you’re dry humping her at 2 a.m. every single night.
But ultimately, it’s not a disorder unless it’s causing trouble, Dr. Cramer Bornemann says. If you’re concerned, see a sleep doctor—preferably someone who specializes in the neurobehavioral aspects of sleep medicine, he says.